This relates generally to erasable memories, such as flash and electrically erasable read only memories (EEPROMs).
Erasable memories may have erasable elements that can become unreliable after a predetermined number of erase cycles. Thus, if one cell is erased dramatically more than other cells, that cell may be prone to earlier failure than the rest of the memory. As cells fail, the life of the memory is reduced.
Wear leveling attempts to level out the erasures across sets of cells so that the cells have the greatest useful life. Generally, the wear leveling works on the block level by preventing one block from getting erased more times than other blocks.